Javascript charting library for huge data

In their example, the dygraphs library handles six thousand data points in a very fast manner. Perhaps that would be suitable for your needs?

It is based on Canvas with excanvas for IE support.

The ZingChart JavaScript charting library might be worth checking out. It was specifically built for big data and offers some great features to ensure fast, stable renders without losing interactivity.

Here is a demo that renders 100k points in under one second. And if you'd like to make some comparisons, there is also the ZingChart Vs. demo (note the warning on the top right- some libs can mess with your browser).

Full disclosure, I'm on the ZingChart team. I'm happy to answer any questions you might have about the library.

ECharts can handle a large amount of data (I've tested them with 100k points x 3 series).

It is an open source and free to use (Apache 2.0) library. Here is an example of a large scale data chart https://ecomfe.github.io/echarts-examples/public/editor.html?c=candlestick-large

If you would like to use Echarts line series type with a large amount of data you should turn on "sampling" http://echarts.apache.org/option.html#series-line.sampling to aggregate data points. Another useful option would be showSymbol: false which will also boost performance.